Semiconductor device having a floating semiconductor zone

ABSTRACT

A semiconductor device includes a first trench and a second trench extending into a semiconductor body from a surface. A body region of a first conductivity type adjoins a first sidewall of the first trench and a first sidewall of the second trench, the body region including a channel portion adjoining to a source structure and being configured to be controlled in its conductivity by a gate structure. The channel portion is formed at the first sidewall of the second trench and is not formed at the first sidewall of the first trench. An electrically floating semiconductor zone of the first conductivity type adjoins the first trench and has a bottom side located deeper within the semiconductor body than the bottom side of the body region.

CROSS-REFERENCE TO RELATED APPLICATIONS

This Utility Patent Application is a continuation application of U.S.application Ser. No. 13/610,240, filed Sep. 11, 2012, which is adivisional application of U.S. application Ser. No. 12/506,844, filedJul. 21, 2009, now U.S. Pat. No. 8,264,033, issued Sep. 11, 2012, all ofwhich are incorporated herein by reference.

BACKGROUND OF THE INVENTION

In semiconductor devices such as Insulated Gate Bipolar Transistors(IGBTs) requirements such as low on-state voltage, low short circuitcurrent, low impact of changes of a collector-emitter-voltage on a gateduring switching conditions, low impact of changes of an internal chargecarrier distribution on the gate, in particular during switch-on and inshort-circuit, and high reverse blocking capability and reliability haveto be met. A trade-off between these requirements is common practice.

A need exists for a device having a low impact of changes of an internalcharge carrier distribution on the gate, a high reverse blockingcapability and a high device reliability.

For these and other reasons there is a need for the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a furtherunderstanding of embodiments and are incorporated in and constitute apart of this specification. The drawings illustrate embodiments andtogether with the description serve to explain principles ofembodiments. Other embodiments and many of the intended advantages ofembodiments will be readily appreciated as they become better understoodby reference to the following detailed description. The elements of thedrawings are not necessarily to scale relative to each other. Likereference numerals designate corresponding similar parts.

Features and advantages of embodiments will be apparent from thefollowing description with reference to the accompanying drawings. Thedrawings are not necessarily to scale and emphasis is placed uponillustrating the principles. The features of the various illustratedembodiments can be combined in any way unless they exclude each other.

FIG. 1 illustrates one embodiment of a semiconductor device including across-sectional view of a portion of an IGBT including an electricallyfloating semiconductor zone adjoining to a trench.

FIG. 2 illustrates a portion of the cross-sectional view of the IGBTillustrated in FIG. 1.

FIG. 3 illustrates a schematic plan view of a portion of an IGBT cellarray including an electrically floating semiconductor zone according toan embodiment.

FIG. 4 illustrates a cross-sectional view of a portion of an IGBTincluding a gate electrode structure within a trench and a channelportion formed on one sidewall of the trench.

FIG. 5 illustrates a cross-sectional view of a portion of an IGBTincluding an electrically floating semiconductor zone adjoining to atrench, wherein a bottom side of the trench is arranged deeper within asemiconductor body than the bottom side of the electrically floatingsemiconductor zone.

FIG. 6 illustrates a cross-sectional view of a portion of an IGBTincluding an electrically floating semiconductor zone adjoining to abottom side of a trench.

FIG. 7 illustrates a cross-sectional view of a portion of an IGBTincluding an electrically floating semiconductor zone adjoining toopposing sidewalls of a trench.

FIG. 8 illustrates a cross-sectional view of a portion of an IGBTincluding an electrically floating semiconductor zone adjoining to atrench filled with dielectric material.

FIG. 9 illustrates a cross-sectional view of a portion of an IGBTincluding an electrically floating semiconductor zone adjoining to atrench filled with dielectric material, wherein a width of the trenchfilled with dielectric material is smaller than the width of the trenchincluding a gate electrode structure.

FIG. 10 illustrates a cross-sectional view of a portion of an IGBTincluding an electrically floating semiconductor zone adjoining to atrench and a first arrangement of an electrode structure within thetrench.

FIG. 11 illustrates a cross-sectional view of a portion of an IGBTincluding an electrically floating semiconductor zone adjoining to atrench and a second arrangement of an electrode structure within thetrench.

FIG. 12 illustrates a cross-sectional view of a portion of an IGBTincluding an electrically floating semiconductor zone adjoining to atrench and a third arrangement of an electrode structure within thetrench.

FIG. 13 illustrates a cross-sectional view of a portion of an IGBTincluding an electrically floating semiconductor zone adjoining to atrench and a fourth arrangement of an electrode structure within thetrench.

FIG. 14 illustrates a cross-sectional view of a portion of an IGBTincluding an electrically floating semiconductor zone adjoining to atrench and a first arrangement of a semiconductor zone adjoining to theelectrically floating semiconductor zone.

FIG. 15 illustrates a cross-sectional view of a portion of an IGBTincluding an electrically floating semiconductor zone adjoining to atrench and a second arrangement of a semiconductor zone adjoining to theelectrically floating semiconductor zone.

FIG. 16 illustrates a cross-sectional view of a portion of an IGBTincluding a first arrangement of an electrically floating semiconductorzone adjoining to a trench at a bottom portion of the trench.

FIG. 17 illustrates a cross-sectional view of a portion of an IGBTincluding a second arrangement of an electrically floating semiconductorzone adjoining to a trench at a bottom portion of the trench.

FIG. 18 illustrates a cross-sectional view of a portion of an IGBTincluding an electrically floating semiconductor zone adjoining to abottom side of a trench filled with dielectric material.

FIG. 19 illustrates a cross-sectional view of a portion of an IGBTincluding an electrically floating semiconductor zone adjoining to atrench and a first arrangement of a segmented electrode structure.

FIG. 20 illustrates a cross-sectional view of a portion of an IGBTincluding an electrically floating semiconductor zone adjoining to atrench and a second arrangement of a segmented electrode structure.

DETAILED DESCRIPTION OF THE DRAWINGS

In the following Detailed Description, reference is made to theaccompanying drawings, which form a part hereof, and in which is shownby way of illustration specific embodiments in which the invention maybe practiced. In this regard, directional terminology, such as “top,”“bottom,” “front,” “back,” “leading,” “trailing,” etc., is used withreference to the orientation of the Figure(s) being described. Becausecomponents of embodiments can be positioned in a number of differentorientations, the directional terminology is used for purposes ofillustration and is in no way limiting. It is to be understood thatother embodiments may be utilized and structural or logical changes maybe made without departing from the scope of the present invention. Thefollowing detailed description, therefore, is not to be taken in alimiting sense, and the scope of the present invention is defined by theappended claims.

FIG. 1 illustrates a cross-sectional view of a semiconductor deviceincluding a portion of an IGBT 100 according to one embodiment. IGBT 100includes a first trench 101 and a second trench 102 extending into asemiconductor body 103 from a surface 104 of the semiconductor body 103.Within the first trench 101 an insulating structure 105 and an electrodestructure 106 are formed. Within the second trench a gate electrodestructure 107 and a gate dielectric structure 108 are formed.

A body region 109 of p-type adjoins to a first sidewall 110 of the firsttrench 101 and to a first sidewall 111 of the second trench 102. Asource structure 112 of n-type adjoins to the first sidewall 111 and toa second sidewall 113 of the second trench 102. Source structure 112 iselectrically coupled to an emitter contact 114 and the emitter contact114 is further electrically coupled to the body region 109 via a p-typecontact region 115 and to the electrode structure 106 within the firsttrench 101. A channel portion 116 that is controlled in its conductivityby the gate electrode structure 107 is formed at the first sidewall 111and at the second sidewall 113 of the second trench 102. The channelportion 116 is part of the body region 109 and adjoins to the sourcestructure 115 at a top end and to an n-type base zone 117 at a bottomend. A p-type collector region 118 adjoining to a bottom side of thebase zone 117 is electrically coupled to a collector contact 119.

An electrically floating semiconductor zone 120 of p-type adjoins to asecond sidewall 121 of the first trench 101. In the embodimentillustrated in FIG. 1, a distance d₁ from the surface 104 to a bottomside of the electrically floating semiconductor zone 120 is larger thana distance d₂ from the surface 104 to a bottom side of the first trench101. According to other embodiments, the distance d₁ may be equal to orless than the distance d₂. The electrically floating semiconductor zone120 counteracts the occurrence of high peak values of an electric fieldat a bottom edge of the first and second trenches 101, 102 in reverse orshort-circuit mode. The electrically floating semiconductor zone 120furthermore improves flooding of hole carriers within the semiconductorbody 103 in an area of the body region 109 and the base zone 117 belowbody region 109. These hole carriers may be conducted along the firsttrench between the emitter contact 114 and the collector contact 119. Inthe embodiment illustrated in FIG. 1, the insulating structure 105 andthe gate dielectric structure 108 may be of a same thickness and/ormaterial, e.g., they may be formed in same processes. The electrodestructure 106 within the first trench 101 is electrically coupled to theemitter contact 114. Thus, an electric current due to hole carriersconducted along the first trench 101 results in a lower feedback on thegate electrode structure 107 controlling the conductivity within channelportion 116 than in an arrangement including the gate electrodestructure 107 not only in the second trench 102 but also in the firsttrench 101. In latter case, the hole current would cause a feedback onthe gate electrode structure in the first trench. In the embodimentillustrated in FIG. 1, a low feedback of a hole current on the gateelectrode structure 107 controlling the conductivity within the channelportion 116 is achieved by omitting the source structure at the firstsidewall 110 of the first trench 101 and by electrically coupling theelectrode structure 106 within the first trench 101 to the emittercontact 114.

According to other embodiments, lowering the feedback of the holecurrent on the gate electrode structure 107 may be achieved byalternative measures of equal effect such as increasing a thickness ofthe insulating structure 105 within the first trench 101, i.e. reducinga capacitive coupling between the body region 109 and the base region117 on the one side and the electrode structure 106 within the firsttrench 101 on the other side, electrically coupling the electrodestructure 106 within the first trench 101 to a region different from thegate electrode structure 107 within the second trench 102, i.e.electrically decoupling the electrode structure 106 within the firsttrench 101 from the gate electrode structure 107 within the secondtrench 102.

In the embodiment illustrated in FIG. 1, the body region 109, thecollector region 118 and the electrically floating semiconductor zone120 are of p-type, whereas the source structure 112 and the base region117 are of n-type. According to other embodiments the type of dopant,i.e. p-type or n-type, of these regions may also be vice versa.

The semiconductor body 103 may be of a semiconductor material such asSi, SiGe, SiC or a combination thereof, for example. The semiconductorbody 103 may include a semiconductor substrate and one or a plurality ofepitaxial layers. As an example, the base zone 117 may be an epitaxiallayer formed on the collector region 118 constituting the semiconductorsubstrate. A thickness of the base zone may be appropriately chosen tomeet the requirements of a desired device voltage class.

The emitter contact 114 on the surface 104 of the IGBT 100, e.g., on afront side of the IGBT 100, may be formed of a metal such as Al, Cu, Ag,Pd or a combination thereof Likewise, the collector contact may beformed of a metal such as as Al, Cu, Ag, Pd or a combination thereof.

Doped semiconductor regions such as body region 109, source zone 112 andelectrically floating semiconductor zone 120 may be formed by implant ofdopants into semiconductor body 103 and annealing or by diffusion ofdopants into the semiconductor body 103, for example.

The term electrically floating used herein refers to a semiconductorregion that is electrically decoupled from its surrounding, e.g., by adielectric insulation or by a junction insulation such as a pn-junction.

In the embodiment illustrated in the schematic cross-sectional view ofFIG. 1, the first trench 101 is arranged next to opposing sides of thesecond trench 102, one of the first trenches 101 is arranged opposed tothe first sidewall 111 of the second trench 102 and another one of thefirst trenches 101 is arranged opposed to the second sidewall 113 of thesecond trench 103. IGBT 100 may include one or a plurality of activecells, wherein each cell may include the first and second trenches 101,102 in the shape of stripes, for example. According to anotherembodiment, the cells may also be of square, rectangular or circularshape including trenches in the shape of a grid or ring, for example.

In the embodiment illustrated in the schematic cross-sectional view ofFIG. 1, the first trench 101 and the second trench 102 extend to a samedepth into semiconductor body 103. According to other embodiments, thesetrenches may have different depths. IGBT 100 may include furtherinsulating regions such as regions 130 a, 130 b.

FIG. 2 illustrates a portion of the cross-sectional view of the IGBT 100of FIG. 1. In particular, in FIG. 2 and subsequent figures redundantdevice portions such as one of two symmetric portions of an IGBT cellare omitted.

FIG. 3 is a schematic plan view of a portion of an IGBT cell arrayarrangement including square-shaped cells according to an embodiment. Across-sectional view along a cut line AA′ may correspond to theschematic cross-sectional view illustrated in FIG. 1. IGBT 200 includesa second trench 202 in grid-form having a gate electrode structure 207and a gate dielectric structure 208. A body region 209 in the shape of asquare loop adjoins to a first sidewall 211 of the second trench 202. Afirst trench 201 in the shape of a square loop including an electrodestructure 206 and an insulating structure 205 adjoins to the body region209. An interface between the first trench 201 and the body region 209such as the first sidewall 110 illustrated in the cross-sectional viewof FIG. 1 is not visible in FIG. 3 due to coverage by an emitter contact214 electrically coupled to the electrode structure 206, body region 206and a source zone. A source zone corresponding to source zone 112illustrated in the cross-sectional view of FIG. 1 is not depicted in theplan view of FIG. 3. Instead, body region 206 is illustrated. Anelectrically floating square shaped semiconductor zone 220 adjoins thefirst trench 202. In the illustrated portion of IGBT 200 in FIG. 3, fourIGBT cells are depicted. IGBT 200 may include more cells thanillustrated in FIG. 3.

In the various embodiments illustrated above and below, similar elementswill be denoted by similar reference signs. For example, an element suchas the first trench 101 in FIG. 1 will be denoted by reference signs301, 331, 361, 401, 431, 461, 491, 521, 551, 581, 611, 641, 671, 701,731, 761, 791 in the various embodiments described below. With regard toelements illustrated in FIGS. 4 to 20, reference is also taken tosimilar elements described above with regard to the embodiment of FIG.1.

FIG. 4 illustrates a cross-sectional view of a portion of an IGBT 300.Similar to IGBT 100 illustrated in FIG. 1, IGBT 300 includes asemiconductor body 303, an insulating structure 305 and an electrodestructure 306 within first trenches 301, a p-type body region 309, ann-type source zone 312, a p-type contact region 315, an emitter contact314, a p-type electrically floating semiconductor zone 320, an n-typebase zone 317, a p-type collector region 318 and a collector contact319.

IGBT 300 includes two second trenches 302 arranged next to each other,each of which including a gate dielectric structure 308 and a gateelectrode structure 307. Between opposing sidewalls 313 of the twosecond trenches 302, body region 319 is omitted. Thus, a channel portion316 is only formed on one of two opposing sidewalls of each of the twosecond trenches 302, in particular that sidewall 311 of each of the twosecond trenches 302 which adjoins to the body region 309. The embodimentillustrated in FIG. 4 provides the benefit of a low on-state resistance.Yet another benefit of the embodiment disclosed in FIG. 4 is an improvedconductivity, e.g., conductivity of polysilicon, of the gate electrodestructure 307 within the second trenches 302, in particular in case of agate electrode structure 307 of polysilicon that has not been dopedin-situ. When increasing the distance between the two second trenches302, a higher feedback on the gate electrode structure 307 may becontinuously achieved.

FIG. 5 illustrates a cross-sectional view of a portion of an IGBT 330.Similar to IGBT 100 illustrated in FIG. 1, IGBT 330 includes asemiconductor body 333, an insulating structure 335 and an electrodestructure 336 within a first trench 331, a gate dielectric structure 338and a gate electrode structure 337 within a second trench 332, a p-typebody region 339 including a channel portion 346, an n-type source zone342, a p-type contact region 345, an emitter contact 344, an n-type basezone 347, a p-type collector region 348 and a collector contact 349.

IGBT 330 includes a p-type electrically floating semiconductor zone 350having a bottom side in a depth d₁ with regard to a surface 334 of thesemiconductor body 333 which is smaller than the depth d₂ of the bottomside of the first trench 331.

FIG. 6 illustrates a cross-sectional view of a portion of an IGBT 360.Similar to IGBT 100 illustrated in FIG. 1, IGBT 360 includes asemiconductor body 363, an insulating structure 365 and an electrodestructure 366 within a first trench 361, a gate dielectric structure 368and a gate electrode structure 367 within a second trench 362, a p-typebody region 369 including a channel portion 376, an n-type source zone372, a p-type contact region 375, an emitter contact 374, an n-type basezone 377, a p-type collector region 378 and a collector contact 379.

IGBT 360 includes a p-type electrically floating semiconductor zone 350that adjoins to a bottom side of the first trench 361. The embodimentillustrated in FIG. 6 is configured to counteract the occurrence of highpeak values of an electric field at a bottom edge of the first andsecond trenches 361, 362 in reverse or short-circuit mode.

FIG. 7 illustrates a cross-sectional view of a portion of an IGBT 400.Similar to IGBT 100 illustrated in FIG. 1, IGBT 400 includes asemiconductor body 403, an insulating structure 405 and an electrodestructure 406 within a first trench 401, a gate dielectric structure 408and a gate electrode structure 407 within a second trench 402, a p-typebody region 409 including a channel portion 416, an n-type source zone412, a p-type contact region 415, an emitter contact 414, an n-type basezone 417, a p-type collector region 418 and a collector contact 419.

IGBT 400 includes a p-type electrically floating semiconductor zone 420that adjoins to a bottom side and to opposing sidewalls, i.e. a firstsidewall 410 and a second sidewall 421, of the first trench 401. Inparticular, p-type electrically floating semiconductor zone 420 adjoinsto the second sidewall 421 and encompasses a lower portion of the firsttrench 401 such that it adjoins to the bottom side and to a lowerportion of the first sidewall 410 of the first trench 401. Oneembodiment illustrated in FIG. 7 is configured to counteract theoccurrence of high peak values of an electric field at a bottom edge ofthe first and second trenches 401, 402 in reverse or short-circuit mode.

FIG. 8 illustrates a cross-sectional view of a portion of an IGBT 430.Similar to IGBT 100 illustrated in FIG. 1, IGBT 430 includes asemiconductor body 433, a gate dielectric structure 438 and a gateelectrode structure 437 within a second trench 432, a p-type body region439 including a channel portion 446, an n-type source zone 442, a p-typecontact region 445, an emitter contact 444, an n-type base zone 447, ap-type collector region 448 and a collector contact 449.

IGBT 430 includes a first trench 431 filled with an insulating material452 such as SiO₂. Thus, a thin dielectric layer within the first trench431 is omitted, the reliability of which, different from a gatedielectric, may only be verified with effort.

FIG. 9 illustrates a cross-sectional view of a portion of an IGBT 460.Similar to IGBT 100 illustrated in FIG. 1, IGBT 460 includes asemiconductor body 463, a gate dielectric structure 468 and a gateelectrode structure 467 within a second trench 462, a p-type body region469 including a channel portion 476, an n-type source zone 472, a p-typecontact region 475, an emitter contact 474, an n-type base zone 477, ap-type collector region 478 and a collector contact 479.

IGBT 460 includes a first trench 461 filled with an insulating material482 such as SiO₂. Furthermore, a width w₁ of the first trench 461 issmaller than the width w₂ of the second trench 462. Thus, filling thefirst trench 461 with the insulating material 482 and stress induced bythe first trench 461 and its filling may be beneficial with regard to atrench of larger width.

FIG. 10 illustrates a cross-sectional view of a portion of an IGBT 490.Similar to IGBT 100 illustrated in FIG. 1, IGBT 490 includes asemiconductor body 493, an insulating structure 495 and an electrodestructure 496 within a first trench 491, a gate dielectric structure 498and a gate electrode structure 497 within a second trench 492, a p-typebody region 499 including a channel portion 506, an n-type source zone502, a p-type contact region 505, an emitter contact 504, an n-type basezone 507, a p-type collector region 508 and a collector contact 509.

The insulating structure 495 within the first trench 491 of IGBT 490 hasa thickness t₁ larger than the thickness t₂ of the gate dielectricstructure 498. The increased thickness of the insulating structure 495within the first trench 491 provides the benefit of an increased safetymargin with regard to a breakdown voltage of this insulating structurethat may be applied during operation conditions.

FIG. 11 illustrates a cross-sectional view of a portion of an IGBT 520.Similar to IGBT 100 illustrated in FIG. 1, IGBT 520 includes asemiconductor body 523, an insulating structure 525 and an electrodestructure 526 within a first trench 521, a gate dielectric structure 528and a gate electrode structure 527 within a second trench 522, a p-typebody region 529 including a channel portion 536, an n-type source zone532, a p-type contact region 535, an emitter contact 534, anelectrically floating semiconductor zone 540, an n-type base zone 537, ap-type collector region 538 and a collector contact 539.

The insulating structure 525 within the first trench 521 of IGBT 520 hasa thickness t₁ larger than the thickness t₂ of the gate dielectricstructure 528. The increased thickness of the insulating structure 525within the first trench 521 provides an increased safety margin withregard to a breakdown voltage of this insulating structure that may beapplied during operation conditions. Furthermore, the electrodestructure 526 within the first trench 521 may be electrically floatingas illustrated in FIG. 11. The electrode structure 526 within the firsttrench 521 may also be electrically coupled to the emitter contact 534or to the gate electrode structure 527 within the second trench 522.

FIG. 12 illustrates a cross-sectional view of a portion of an IGBT 550.Similar to IGBT 520 illustrated in FIG. 11, IGBT 550 includes asemiconductor body 553, an insulating structure 555 and an electrodestructure 556 within a first trench 551, a gate dielectric structure 558and a gate electrode structure 557 within a second trench 552, athickness t₁ of the insulating structure 555 being larger than thethickness t₂ of the gate dielectric structure 558, a p-type body region559 including a channel portion 566, an n-type source zone 562, a p-typecontact region 565, an emitter contact 564, an electrically floatingsemiconductor zone 570, an n-type base zone 567, a p-type collectorregion 568 and a collector contact 569.

The electrode structure 556 extends over the surface 524 ofsemiconductor body 554 to the electrode.

FIG. 13 illustrates a cross-sectional view of a portion of an IGBT 580.Similar to IGBT 520 illustrated in FIG. 11, IGBT 580 includes asemiconductor body 583, an insulating structure 585 and an electrodestructure 586 within a first trench 581, a gate dielectric structure 588and a gate electrode structure 587 within a second trench 582, athickness t₁ of the insulating structure 585 being larger than thethickness t₂ of the gate dielectric structure 588, a p-type body region589 including a channel portion 596, an n-type source zone 592, a p-typecontact region 595, an emitter contact 594, an electrically floatingsemiconductor zone 600, an n-type base zone 597, a p-type collectorregion 598 and a collector contact 599.

The electrode structure 586 is electrically coupled to the electricallyfloating semiconductor zone 600 via a conductive strap 603, e.g., ametal strap or doped semiconductor strap, at the surface 584 of thesemiconductor body 583. Thus, the electrode structure 586 iselectrically floating similar to the semiconductor zone 600. Theconductive strap 603 may be formed in different ways, e.g., by utilizingmetal layers and contact plugs. This also applies to the embodimentillustrated in FIG. 12.

FIG. 14 illustrates a cross-sectional view of a portion of an IGBT 610.Similar to IGBT 550 illustrated in FIG. 12, IGBT 610 includes asemiconductor body 613, an insulating structure 615 and an electrodestructure 616 within a first trench 611, a gate dielectric structure 618and a gate electrode structure 617 within a second trench 612, athickness t₁ of the insulating structure 611 being larger than thethickness t₂ of the gate dielectric structure 618, a p-type body region619 including a channel portion 626, an n-type source zone 622, a p-typecontact region 625, an emitter contact 624, an electrically floatingsemiconductor zone 630, an n-type base zone 627, a p-type collectorregion 628 and a collector contact 629.

In addition to IGBT 550 illustrated in FIG. 12, IGBT 610 includes ann-type semiconductor zone 634 adjoining to a bottom side of the firsttrench 611. A dopant density of the n-type semiconductor zone 634 islarger than the dopant density of the n-type base zone 627. As anexample the dopant density of the semiconductor zone 634 may be a factorof 10, 100 or even 1000 larger than the dopant density of the n-typebase zone 627. The n-type semiconductor zone 634 is configured tolocalize a breakdown region during a reverse mode of IGBT 610 to abottom region of the first trench 611 away from the gate electrodestructure within the second trench 612. The n-type semiconductor zone634 may be formed by implant of dopants via a bottom side of the firsttrench 611 prior to filling up this trench. In case of a semiconductorbody 613 made of silicon, an implant dose may be in the order of 10¹²cm⁻².

FIG. 15 illustrates a cross-sectional view of a portion of an IGBT 640.Similar to IGBT 610 illustrated in FIG. 14, IGBT 640 includes asemiconductor body 643, an insulating structure 645 and an electrodestructure 646 within a first trench 641, a gate dielectric structure 648and a gate electrode structure 647 within a second trench 642, athickness t₁ of the insulating structure 641 being larger than thethickness t₂ of the gate dielectric structure 648, a p-type body region649 including a channel portion 656, an n-type source zone 652, a p-typecontact region 655, an emitter contact 654, an electrically floatingsemiconductor zone 660, an n-type semiconductor zone 664, an n-type basezone 657, a p-type collector region 658 and a collector contact 659.

The n-type semiconductor zone 664 adjoins to both a bottom side of thefirst trench 641 and the bottom side of the electrically floatingsemiconductor zone 660.

FIG. 16 illustrates a cross-sectional view of a portion of an IGBT 670.Similar to IGBT 460 illustrated in FIG. 9, IGBT 670 includes asemiconductor body 673, a first trench 671 filled with an insulatingmaterial 692, a gate dielectric structure 678 and a gate electrodestructure 677 within a second trench 672, a p-type body region 679including a channel portion 686 and, in addition, a p-type electricallyfloating body region 679′, an n-type source zone 682, a p-type contactregion 685, an emitter contact 684, a p-type electrically floatingsemiconductor zone 690, an n-type base zone 687, a p-type collectorregion 688 and a collector contact 689.

IGBT 670 includes a plurality of first trenches 671 arranged next toeach other. Furthermore, the p-type electrically floating semiconductorzone 690 does not adjoin to the surface 674 of the semiconductor body673, but merely surrounds a lower portion of the first trench 671. Thesemiconductor zone 690 may be formed by implant of dopants into thesemiconductor body 673 via a bottom side of the first trench 671 priorto filling up this trench and subsequent annealing.

FIG. 17 illustrates a cross-sectional view of a portion of an IGBT 700.Similar to IGBT 670 illustrated in FIG. 16, IGBT 700 includes asemiconductor body 703, a first trench 701 filled with an insulatingmaterial 722, a gate dielectric structure 708 and a gate electrodestructure 707 within a second trench 702, a p-type body region 709including a channel portion 716, a p-type electrically floating bodyregion 709′, an n-type source zone 712, a p-type contact region 715, anemitter contact 715, a p-type electrically floating semiconductor zone720, an n-type base zone 717, a p-type collector region 718 and acollector contact 719.

The p-type floating semiconductor zone 720 adjoining to one of the firsttrenches IGBT 700 overlaps with the p-type electrically floatingsemiconductor zone 720 associated with a neighboring one of the firsttrenches 701. Adjustment of overlap or non-overlap of the electricallyfloating semiconductor zones such as zones 690 illustrated in FIG. 16(an example of overlap) may be determined by a thermal budget whenannealing the implanted dopants of these zones.

FIG. 18 illustrates a cross-sectional view of a portion of an IGBT 730.Similar to IGBT 100 illustrated in FIG. 1, IGBT 730 includes asemiconductor body 733, a gate dielectric structure 738 and a gateelectrode structure 737 within a second trench 732, a p-type body region739 including a channel portion 746, an n-type source zone 742, a p-typecontact region 745, an emitter contact 744, a p-type electricallyfloating semiconductor zone 750, an n-type base zone 747, a p-typecollector region 748 and a collector contact 749.

The first trench 731 is filled with an insulating material 752 such asSiO₂. Furthermore, a width w₁ of the first trench 731 is larger than thewidth w₂ of the second trench 732. The p-type electrically floatingsemiconductor zone 750 is arranged below the first trench 731 andadjoins to a bottom side of the first trench 731.

FIG. 19 illustrates a cross-sectional view of a portion of an IGBT 760.Similar to IGBT 100 illustrated in FIG. 1, IGBT 760 includes asemiconductor body 763, an insulating structure 765 and an electrodestructure 766 within a first trench 761, a gate dielectric structure 768and a gate electrode structure 767 within a second trench 762, a p-typebody region 769 including a channel portion 776, an n-type source zone772, a p-type contact region 775, an emitter contact 774, a p-typeelectrically floating semiconductor zone 780, an n-type base zone 777, ap-type collector region 778 and a collector contact 779.

The gate electrode structure 767 of IGBT 760 constitutes an upperelectrode of an electrode structure 784, the upper electrode 767 beingelectrically insulated from a lower electrode 785. The lower electrode785 may be electrically floating or electrically coupled to an auxiliarysupply, e.g., to the emitter voltage. A positive auxiliary supplyvoltage may increase the accumulation of hole carriers withinsemiconductor body 763 during operation conditions and may reduce asaturation voltage between the emitter contact 774 and the collectorcontact 779. The gate electrode structure 767 may extend from thesurface 764 to a bottom side of the body region 769 or even deeper intothe semiconductor body 763. Reducing the vertical dimensions of the gateelectrode structure 767 within the second trench 762 by segmenting theelectrode structure in two or even more parts allows to reduce thecapacitance between gate and drain, i.e. between the gate electrodestructure 776 and the n-type base zone 777.

FIG. 20 illustrates a cross-sectional view of a portion of an IGBT 790.Similar to IGBT 760 illustrated in FIG. 19, IGBT 790 includes asemiconductor body 793, an insulating structure 795 and an electrodestructure 796 within a first trench 791, a gate dielectric structure 798and an electrode structure 814 including a gate electrode structure 797as an upper electrode and a lower electrode 815 within a second trench792, a p-type body region 799 including a channel portion 806, an n-typesource zone 802, a p-type contact region 805, an emitter contact 804, ap-type electrically floating semiconductor zone 810, an n-type base zone807, a p-type collector region 808 and a collector contact 809.

An electrode 816 within the first trench 791 is segmented into twoelectrodes electrically insulated from each other and includes theelectrode structure 796 as an upper electrode and a lower electrode 817.The lower electrodes 815, 817 in the first and second trenches 791, 792may be formed in same processing steps. Likewise, the upper electrodes796, 797 in the first and second trenches 791, 792 may also be formed insame processing steps. Thereby, the manufacturing process may besimplified resulting in a same electrode arrangement in the first andsecond trenches 791, 792. The upper electrodes 796. 797 of the first andsecond trenches 791, 792 may be electrically coupled to each other.These electrodes may also be electrically decoupled.

It is to be understood that the features of the various embodimentembodiments described herein may be combined with each other, unlessspecifically noted otherwise.

Although specific embodiments have been illustrated and describedherein, it will be appreciated by those of ordinary skill in the artthat a variety of alternate and/or equivalent implementations may besubstituted for the specific embodiments shown and described withoutdeparting from the scope of the present invention. This application isintended to cover any adaptations or variations of the specificembodiments discussed herein. Therefore, it is intended that thisinvention be limited only by the claims and the equivalents thereof.

What is claimed is:
 1. A semiconductor device, comprising: a firsttrench and a second trench extending into a semiconductor body from asurface; a body region of a first conductivity type adjoining a firstsidewall of the first trench and a first sidewall of the second trench,the body region including a channel portion adjoining a source structureand being configured to be controlled in its conductivity by a gatestructure, wherein the channel portion is formed at the first sidewallof the second trench and is not formed at the first sidewall of thefirst trench; and an electrically floating semiconductor zone of thefirst conductivity type adjoining to the first trench and having abottom side located deeper within the semiconductor body than a bottomside of the body region, wherein each of the first and second trenchincludes an insulating structure and an electrode structure.
 2. Thedevice of claim 1, wherein a thickness of the insulating structurewithin the first trench is larger than the thickness of the insulatingstructure within the second trench.
 3. The semiconductor device of claim1 wherein the electrode structure in the first trench is electricallyfloating.
 4. The semiconductor device of claim 3, wherein the electrodestructure within the first trench is electrically coupled to theelectrically floating semiconductor zone via a conductive strap.
 5. Thesemiconductor device of claim 1, wherein the electrode structure in thefirst trench is electrically coupled to the electrode structure in thesecond trench.
 6. The semiconductor device of claim 1, wherein theelectrode structure in the first trench is electrically coupled to thesource structure formed within the body region.
 7. The semiconductordevice of claim 1, wherein the electrode structure in the second trenchis segmented into at least two electrodes electrically insulated fromeach other.
 8. The semiconductor device of claim 7, wherein theelectrode structure in the first trench is segmented into at least twoelectrodes electrically insulated from each other.
 9. A semiconductordevice, including: a first trench and a second trench extending into asemiconductor body from a surface; a body region of a first conductivitytype adjoining to a first sidewall of the first trench and to a firstsidewall of the second trench, a dopant density of a body portionadjoining to the first sidewall of the second trench being lower thanthe dopant density of the body portion adjoining the first sidewall ofthe first trench; and an electrically floating semiconductor zone of thefirst conductivity type adjoining to the first trench and having abottom side located deeper within the semiconductor body than the bottomside of the body region.
 10. The semiconductor device of claim 9,wherein a first semiconductor zone of a second conductivity type adjoinsto a bottom side of the first trench, the first semiconductor zonehaving a larger dopant density than a second semiconductor zone of thesecond conductivity type adjoining to a bottom side of the body region.11. The semiconductor device of claim 10, wherein the firstsemiconductor zone adjoins to a bottom side of the electrically floatingsemiconductor zone of the first conductivity type.
 12. A semiconductordevice, comprising: a first trench and a second trench extending into asemiconductor body from a surface; a body region of a first conductivitytype adjoining a first sidewall of the first trench and a first sidewallof the second trench, the body region including a channel portionadjoining a source structure and being configured to be controlled inits conductivity by a gate structure, wherein the channel portion isformed at the first sidewall of the second trench and is not formed atthe first sidewall of the first trench, the gate structure beingprovided in the second trench; and an electrically floatingsemiconductor zone of the first conductivity type adjoining to the firsttrench and having a bottom side located deeper within the semiconductorbody than a bottom side of the body region, wherein each of the firstand second trench includes an insulating structure and an electrodestructure being provided in the first trench and electrically coupled toa region different from the gate structure within the second trench. 13.A semiconductor device, including: a first trench and a second trenchextending into a semiconductor body from a surface; a body region of afirst conductivity type adjoining to a first sidewall of the firsttrench and to a first sidewall of the second trench, a dopant density ofa body portion adjoining to the first sidewall of the second trenchbeing lower than the dopant density of the body portion adjoining thefirst sidewall of the first trench; and an electrically floatingsemiconductor zone of the first conductivity type adjoining to the firsttrench and having a bottom side located deeper within the semiconductorbody than the bottom side of the body region, wherein a gate structureis provided in the second trench, and an electrode structure provided inthe first trench is electrically coupled to a region different from thegate structure in the second trench.